Many prior art waste-processing systems are designed for low-solids waste, such as municipal waste, that has a solids content of approximately one percent. High-solids wastes such as manure that have a solids content of approximately five to twelve percent either clog the system or are insufficiently processed. The processing of high-solids waste has typically been performed using a plug flow process that is characterized by a straight-through system.
Prior art waste-processing systems for either high- or low-solids waste use large amounts of purchased energy in the form of electricity or natural gas to generate heat and run pumps to process the wastes because these systems typically exhibit inefficient heating of the waste as it is processed. In addition, prior art waste-processing systems have the added problem of disposing of the products of their processing. It is anticipated that stricter environmental regulations will limit the amount of waste than can be applied to fields as fertilizer because of the phosphates and nitrogen content of the waste. As fields reach their limits, other fields must be found. As the amount of unfertilized land dwindles, either other outlets for waste must be found, or a disposal method that meets the stricter environmental regulations must be developed and used.